The North American species of Psathyrella.

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MEMOIRS OF THE NEW YORK BOTANICAL GARDEN

[VOL. 24

described as elliptic to oblong, rarely ovate, and in another they may be given
as ovate to elliptic rarely oblong, and the difference would likely be of taxonomic
significance. The order in which the descriptive terms appear in the descriptions
has definite significance.
The greatest difficulty is encountered in giving a meaningful description of
the spore in profile view. This stems in part from the spore tending to have a
depression or merely a flattened area just distal to the apiculus. Basically, in
descriptive work, one can consider the spore in optical section as it is attached
to the sterigma and identify a dorsal (upper) line forming the spore outline which
is separate from the ventral (lower) line (see Fig. 9, bottom spore). There is
a tendency for the dorsal line to be humped slightly opposite the flattened (plage)
area of the ventral line. At or near the midportion of the spore the dorsal line
may level off to the spore apex, but the ventral line may show a bulge (or hump)
just distal to the plage area. If a line is drawn across the spore, the peak of
the dorsal hump will be toward the base of the spore and the peak of the ventral
hump will be to its distal side. In other words, the two humps are not lined up
perfectly as seen in a profile optical section of the spore. If this condition is
pronounced, the profile view of the spore is described as inequilateral. In some
genera this term can be applied to many species, but in Psathyrella it is often
obscure. Hence qualifying adjectives have been applied in this work on the
following basis: if the described condition is obscure, as in many species of
Psathyrella, the term "obscurely inequilateral" is applied and as one would
expect, if an intermediate condition existed, an intermediate term (in this case
"somewhat inequilateral") is used. Considerable latitude in applying the terms
is to be allowed, and spores may be expected to vary in profile view from this
basic shape to others such as bean-shaped (depressed on the ventral line). But
the obscurely inequilateral shape in profile is the basic shape of the Psathyrella
spore. Spores of the subgenus Psathyroides are typically oblong in face view but
bean-shaped in profile.
The germ pore at the apex of the spore is a generic feature and like all such
features is not necessarily present in every species-at least as far as can be
detected with the light microscope. As one would expect, it is most poorly
developed on spores with thin walls (0.2 it thick approximately). When present,
the position of the pore is typically apical and usually oriented at right angles
to the long axis of the spore. In some species, however, and these are mainly
among those with dark brown to blackish spores, the "apical pore" may be
oblique to slightly eccentric. Since this is a pronounced feature in the spores of
many species of Coprinus, it is interesting to find the feature here in a rudimentary
state. The size of the germ pore ranges from being so narrow it can hardly be
resolved with the best magnification of the light microscope, to up to 3 K broad
or slightly more. Also, the pore is not a simple hole in the thickened endospore
wall. Rather it often appears to be an area of wall material which does not
develop pigment-hence it appears as a hyaline spot. The thin outer wall typically
extends over the area maintaining the overall curvature of the spore apex. Such
spores cannot legitimately be termed truncate (chopped off) at the apex. If
the area of the pore collapses, however, then the apex becomes invaginated or
flattened to some extent, the spore may be properly termed truncate. On the
other hand, when mounted in KOH the spores of some species bulge at the
apex so that the "pore" projects as a hyaline bubble. P. velutina usually shows
this condition well. It should also be remembered that the term truncate can
be legitimately applied to either end of the spore. In P. hirtosquamulosa the